NASA plans to launch a pair of probes this morning that will gather data of unprecedented detail about our moon’s gravity.

Launch of the twin Grail spacecraft is scheduled for 8:37am EST, from Florida’s Cape Canaveral Air Force Station. If that time fails, NASA has a second window just a few minutes later, at 9:16am.

UPDATE:According to NASA, the launch has been delayed to the second time, 9:16am, due to wind.

UPDATE 2: NASA has announced that, due to “upper level winds,” launch has been pushed back 24 hours.

With a chance of thunderstorms looming, however, the launch only has a 40 percent chance of moving forward without weather delays, reports Space.com. Unfortunately, the forecast is equally grim on Friday, so Grail’s launch may have to wait until the weekend, when conditions are expected to be much better.

If that doesn’t work, Grail has a total of 42 days before the window will close, after October 19.

With the Grail mission, NASA scientists hope to gain a better understanding of the geology and evolutionary history of our moon. Such a study will help researchers discover how the moon was formed 4.6 billion years ago, which will give clues about how other heavenly bodies in our inner solar system came into existence.

“What we’re trying to do with the Grail mission – we’re essentially getting a picture into the interior of the moon,” said Maria Zuber, Grail principal investigator at MIT. “We intend to provide a holistic view of the origin and evolution of the moon, and by extension, how other rocky planets in the inner solar system formed.”

At a cost of $496 million, the twin Grail probes, Grail-A and Grail-B, are set to enter the moon’s orbit simultaneously, and maintain a distance of about 34 miles above the lunar surface. The two probes will circle the moon about 75 to 225 miles apart from each other.

Grail’s destination is still quite a long way off, however, as the mission is taking the most energy efficient path to the moon, meaning it will take until around New Year’s Day for Grail to arrive.

Grail-A and Grail-B will communicate with each other using microwave signals, and be able to measure the distance between one another within less than the width of a human blood cell, according to Sami Asmar, Grail deputy project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

NASA expects Grail to provide massive quantities of invaluable data, which will build upon knowledge gained through previous lunar missions.

“The moon is a fantastic body…in terms of learning about early planets,” Zuber said. “It’s nearby, it’s accessible, and it preserves the record of what early planets are like. Other planets in the inner part of the solar system have gone through the same processes that the moon has gone through. I think in the next five years, we’re going to rewrite the book on our understanding.”